Seen through the cold glare of Sir Alex Ferguson's eyes, Manchester United's games against Liverpool may be bigger occasions but the ones against City will go further to deciding the destination of the championship.

It is 12 months since anyone last took a point at Old Trafford, but Manchester City will go there next Sunday with a little clear sky blue water between themselves and their neighbours. Since Carlos Tevez's frustrations exploded in Munich, Manchester City have played twice and scored eight times.

No side is ever entirely united; there are fault lines in every dressing room. But Roberto Mancini's players have demonstrated that they are not men put off their stride by the exiling of last season's captain and leading scorer.

Aston Villa have a dreadful record in the blue half of Manchester. This was their first league defeat of the season but their 11th in their past dozen games at Eastlands or Maine Road and they could scarcely have been swept away by a more emphatic scoreline. When Shay Given, who like Richard Dunne and Stephen Ireland endured a wretched return to his former club, collided with Mario Balotelli and Micah Richards, he lifted his shirt to reveal the Italian's studs marks reddening on his torso. However, Villa's wounds were more than skin deep.

"It does not matter if you are playing Manchester City or an amateur team, if you defend like this, you will lose games," Alex McLeish, the Villa manager, said. "People will see the scoreline and everyone will think City cut Aston Villa to ribbons. We weren't but what they will see is some horrendous defending."

Now that Wayne Rooney is suspended for the group stages of the European Championship – a phase England have only got through twice in the modern history of the competition – the limelight will shine ever more fiercely on Darren Bent and Gabriel Agbonlahor.

The first had no opportunities to speak of. Agbonlahor had a one-on-one that was well saved by Joe Hart while Villa's goal came from the boot of Stephen Warnock. When the left-back drove his shot in from the underside of Hart's crossbar, his team were three down and City were, temporarily, without a right-back through Richards's head injury.

If hope of a recovery flickered in McLeish's brain, it was extinguished a few minutes later when Adam Johnson and Gareth Barry fed James Milner who curled a beautiful side-footed shot beyond Given. It says something that the Villa keeper barely moved for two of City's goals.

It says something for the standards Mancini demands that Johnson's performance, which saw him play a part in each of the goals, was rated "so-so in the first half" by his manager.

The first was an astonishing effort; a corner from Johnson, headed on by Vincent Kompany. It fell between Richards, who seemed not to know what to do with it, and Balotelli who did, finishing emphatically with a bicycle kick.

"Mario was four or five times on the bench in the last month," Mancini said, "but this time he understood why and now has scored four goals in a row and worked for the team. But we know Mario can change at any moment."

Then it was Johnson's turn to score. Warnock missed his clearance from a long upfield punt by Yaya Touré, the ball fell to Johnson who turned and stabbed it past a stranded goalkeeper.

The third was even simpler and, to McLeish, even more wastefully stupid; a near-post header from an entirely unmarked Kompany that sent Johnson's corner straight into the net. It ensured Manchester City's supporters would go to Old Trafford top of the league, something they would not have expected since the dazzling days of Joe Mercer and Malcolm Allison.